This invention relates generally to space heating and more particularly to a space heating system which utilizes the heat in the exhaust gas of an engine.
More specifically, the invention concerns a space heating system in which a combination of a heat transferring or heat transmitting pipe known as "heat pipe" or thermosyphon is used to receive, at its one end, heat in the exhaust gas flowing through the exhaust pipe of an engine and to transmit this heat to its other end disposed in the air duct thereby to heat air flowing through this duct into a space to be heated.
The space heating system of this invention is applicable to the heating of spaces which are reasonably near fuel-combustion type engines. A typical example of such spaces is an interior space of an engine-driven land vehicle such as a motorcar and a water surface craft.
Systems for heating interior spaces of engine-driven vehicles of the general type mentioned above employing heat pipes with heat receiving or absorbing elements for installation in engine exhaust pipes and heat discharging elements for installation in air ducts are known, as disclosed in Japanese Patent Laid-Open Publication (Kokai) No. 24617/1977. Similar systems are also disclosed in U.S. Pat. No. 4,667,876 to S. Negishi et al.
In such type of system for heating vehicle interiors, the heat pipe itself is of a sealed type, and its interior, after being evacuated is supplied with water or some other working fluid and sealed.
In the case of a heat pipe of this sealed type, in the event that for some reason the temperature within the engine exhaust pipe rises excessively, whereby the vapor pressure of the working fluid within the heat pipe rises excessively, there is the possiblity of damage or rupturing of the heat pipe.